Erythromycin is an antibiotic clinically widely used as an agent for curing infectious diseases caused by Gram-positive bacteria, some Gram-negative bacteria, mycoplasmas, etc. Many derivatives of erythromycin have been produced for improving the biological and/or pharmacodynamic characteristics of erythromycin. As 5-O-desosaminylerythronolide derivatives, 3-O-acyl-5-O-desosaminylerythronolide derivatives, for example, have been disclosed in U.S. Pat. No. 3,923,784. 5-O-desosaminylerythronolide derivatives, however, have been generally considered to be poor in antibacterial activity, and the antibacterial activity of the above-exemplified derivatives is also very weak. An object of the present invention is to provide novel antibiotics having a strong antibacterial activity.